Blood oxygenating apparatus



May 6, 1958 2 Sheets-Sheet 1 Filed May 25. 1956 Arron/v.9

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May 6, 1958 F. GOLLAN BLOOD OXYGENATING APPARATUS 2 SheetsSheet 2 Filed May 25, 1956 INVENTOR. Wan/ i doZZan United StatesPat m 2,833,279 BLOOD OXYGENATING APPARATUS Frank Gollan, Nashville, Tenn., assignor to the United States of America as represented by the Secretary of the Army The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

The present invention relates to extracorporeal circulation devices and more particularly to a method and apparatus for the oxygenation of venous blood in which thelatter is withdrawn from the circulatory system of a living human being or animal, oxygenated, and returned as arterial blood to the body of the human being or animal. v, i

I In all conditions where the diffusion of oxygen through the alveolar membranes of the lungs is prevented, rapid deterioration of the central nervous system results. Respiratory arrest is followed shortly by cardiovascular crisis, ending in death. Thus, lack of oxygen, or anoxia,

not only stops the vital bodily functions, but it also wrecks the body itself.

In clinical conditions with reduced vital, capacity. and pulmonary minute-volume, such as pneumonia, pulmonary edema, massive aelectasis (collapse of the lungs) and paralysis of the respiratory muscles or the respiratory center, the active or passive inhalation of gas mixtures with high oxygen concentration is a life saving procedure. If, however, pulmonary disease has progressed to the point where, the diffusion of oxygen is limited to a small area of intact alveolar epithelium so as to. make full oxygenation of pulmonary arterial blood impossible,- then inhalation methods become ineffective and another means of blood oxygenation has to be sought. 7

In heart surgery, it has been found impractical to merely by-pa'ssthe heart itself without also providing an artificial means to take over the function of blood oxygenation which'is ordinarily performed by the lungs. It is almost fruitless to attempt any kind of operation on the heart and its associated vessels without temporarily relieving the heart of its function of pumping blood with accompanying vigorous expansions and contractions which make delicate surgical procedures and techniques virtually impossible. Withthe prior art devices for artificially assuming the cardio-respiratory functions'it has hardly ever been possible to obtain the highly desired condition of a bloodless operating field in performing heart surgery or open .cardioto'mies. I i

The idea of oxygenating the circulating blood outside the body by artifical means is not new, and the need for a successful blood oxygenating or heart-lung apparatus has been recognized for-many years; In fact, blood ject death from air embolism was almost certain to ensue.

oxygenators are old in the art and a great number of them have been developed during the past eighty years.

As early as 1882, Schroder in Germany made an attempt to oxygenateblood by bubbling oxygen through it. Although this method seems to have been quite successful so far as actual oxygenation of the blood is concerned, it had to be abandoned because the resulting formation of foam and frothing of the blood made a prolonged procedure with this method impossible, since if any gas remained in the blood in the form of bubbles, when the blood was returned to the circulatory system of the sub- During this century, the attack has been to attempt to more or less imitate in an artificial apparatus the physiological mechanism of gas exchange as it normally takes place within the lungs of a human being. Quite a few devices of this type have been constructed in which thin films of venous blood'are spread over large stationary or moving surfaces, such as the inside wall of a rotating cylinder, and the thin film of blood is in this manner exposed to oxygen. If the film is sufliciently thin, the blood will be completely oxygenated without the disadvantage of the formation of foam or frothing which attends the bubbling method with its resultant danger of air embolism.

The prior art devices and methods, thus, have many disadvantages. The earliest method, that of bubbling oxygen through the venous blood to oxygenate it proved fatally defective due to the formation of a fairly stable foam in the blood which could not be successfully eliminated in time for the return of. the blood to the body of the subject. Although the more modern devices in which the attempt has been made to more or less duplicate the conditions which exist in the lungs and to imitate the method of the functioning and operation of the lungs of a hiunan being or an animal have been somewhat successful, these devices have an almost overwhelming number of practical disadvantages which have not been successfully overcome.

Disadvantages and difiiculties existing in these more modern devices stem from the fact that an adequate rate of flow, approximately six liters of blood per minute,

has to be maintained over large surfaces to sufficiently expose the blood to oxygen and that the blood must then be returned to the body without causing hemolysis, or disintegration of the red corpuscles. The devices themselves are necessarily complicated, large, and expensive, incorporating'many moving parts. They employ delicate electronic controls to insure a constant blood level and to provide alternating pressure and suction and require a staff of highly trained technicians for successful operation. The large size of these devices makes it necessary that they be primed with whole donor blood of a type compatible with that of the subject before their operation can begin. Their size also makes necessary the use of a long extracorporeal circuit which increases the chances for coagulation and hemolysis to occur.

It is an object of the instant invention to provide a small and simplified blood oxygenating apparatus utilizing the surface tensionphenomena of dispersion, coalesence and separation to achieve rapid, efficient, and harmless conversion of venous to gas-free arterial blood.

It is another object of this invention to provide a means for withdrawing venous blood from a living human being or animal, oxygenating the blood in an oxygenating apparatus, and returning the resulting arterial blood to the circulatory system of the livingsubjectwithout danger of hemolysis or air embolism. v

Another object of the present invention is to provide a blood oxygenating means utilizing the principle of bubbling oxygen through venous blood of a living subject to convert it to arterial blood and following the bubbling procedure with the effective removal of all ensuingfoarn or froth from the blood without any deleterious effect on the blood and returning the arterial blood to the body of;

. the living subject without resulting damage to its body.

Another object of this invention is to provide a blood oxygenating means that is small in size, inexpensive, and so simple to operate that it may be operated and controlled by one person instead of requiring a large team of highly skilled personnel.

Another object of this invention is to provide a blood oxygenating means having such a small volume and. such a short extracorporeal circuit that it can be successfully primed with a physiological salt solution making priming with Whole donor blood'unnecessary, and lessening the chances for hemolysis or accidents to occur.

Another object of this invention is to provide a blood oxygenating means incorporating no moving parts, electrodes, relays, or magnetic valves for alternating pressure and suction and for controlling the blood level with the attendant complexity, expense, and possible source of error which is created by the employment of these parts.

Another object of thisinvention is to. provide a blood oxygenating means which handles the blood so gently that destruction of the cellular elements is keptto an absolute minimum.

Another object of this invention is to provide a blood oxygenating means having a construction and size small enough that the problem of maintaining a constant blood level does not exist.

A further object of this invention is to provide a blood oxygenating means utilizing a type of construction and materials thatwill permit autoclaving of the apparatus.

A still further object of this invention is to provide a blood oxygenatingmeans combining the features of simplicity of operation, dependability, small volume, and short extracorporeal circuit to yield a device in which the possibility of the occurrence of an accident is extremely remote.

Further objects and a more thorough understanding of the invention may be obtained by referring to the following description and claims taken in conjunction with the accompanying drawings which disclose an illustrative embodiment of the construction forming the basis of the invention and in which- Fig. l is a schematic view showing the blood oxygenating apparatus connected for operation with a living subject; the blood oxygenating apparatus itself is shown in vertical section;

Fig. 2 is a central vertical section of the blood oxygen ating apparatus;

Fig. 3 is a horizontal section taken along the line 33 of Fig. 2; and

Fig. 4 is a horizontal section taken along the line 44 of Fig. 2.

In accordance with the invention, a blood oxygenating environment is provided having means for introducing oxygen into the environment under pressure, means for introducing venous blood taken from a living subject into the environmennand filter means positioned between the means for introducing oxygen and the means for introducing venous blood. In the present preferred embodiment of the invention, the blood oxygenating environment comprises a receptacle, the means for introducing oxygen comprises an oxygen inlet adjacent to the bottom of the receptacle, the means for introducing venous blood comprises a second inlet to the receptacle above the oxygen inlet, and the filter means comprises a filter of controlled pore size between the oxygen inlet and the venous blood inlet. l

In the illustrated embodiment of the invention (Fig. 2), the receptacle comprises a cylindrically. shaped base 5 having a centrally located cylindrical chamber 6 made up of some suitable chemically inert material, such as stainless steel, and a hollow cylinder 7 supported by and directly above the base 5 made up of a chemically inert and transparent material, such as Pyrex glass. The oxygen inlet 8 comprises a short conduit integral with the base 5 and normal to its wall. The venous blood inlet one of the other silicone compounds.

4 9 comprises a short tubular conduit integral with and tangential to the wall of the hollow cylinder 7 (Fig. 3). The filter comprises a chemically inert, hydrophilic, microporous filter disc 10 of controlled pore size made of porcelain or a similar material and is circumferentially surrounded by a liquid-proof sealing and supporting gasket 11 made up of an elastic sealing material, such as silicone rubber. The filter disc 10 with its gasket 11 is supported above the hollow chamber 6 of the base 5 by an inner circumferential lip 12 integral with the inner wallet the base 5. The cylinder 7 is in turn supported on the base 5 by the upper surface of the filter gasket 11. in conformance with the invention, means are provided in the blood oxygenating environment for liquid-gas separation to remove gas bubbles from the blood with an absolute minimum of cellular damage to the blood. Means are also provided for Withdrawing the resulting oxygenated arterial blood from the environment andfor returning it to the body of the living subject from which venous blood was withdrawn. In the illustrated embodiment of the invention, the liquid-gas separation means comprises a closely packed fibrous body embodying a great number of small interstitial spaces and having a multitude of individual fibers coated with an anti-foaming agent, and the means for withdrawing the resulting arterial blood comprises a tubular outlet. 7

As embodied, the means for liquid-gas separation (Fig. 2) comprises a cylindrical tube 13 having an axis coincidental with the axis of the hollow cylinder 7 and a diameter sufficiently smaller than the diameter of the cylinder 7 to create an annular space 14 between the outer surface of the tube 13 and the inner surface of the cylinder 7. The tube 13 includes a sloping support ring 16 integralwith the Wall of the tube 13 and the inner wall of the cylinder 7 to support the tube 13 in its desired location.

andseal the lower chamber 17 of the cylinder 7 from the annular space 14. Thus, the support ring 16, the tube. 13, and cylinder 7 form one integral piece and are made.

of one homogeneous, transparent and chemically inert material, such as Pyrex glass. It has been foundbeneficial to coat the interior of the Pyrex glass cylinder with a chemically inert non-wetting agent, such as a suitable. silicone compound, to prevent the blood from adheriflgjto the inside surface of the cylinder 7. The liquid-gas sep-.

arating means also comprises a closely packed fibrous body 18 of a chemically inert and biologically harmless material, such as stainless steel, plastic fibers, or fiberglass. This fibrous body 18 is compressed until it occupies an appreciably smaller volume from that occupied byits unrestrained shape, and it is then forcibly inserted into the cylindrical tube 13 where it is held firmly in place by its natural tendency to resume its enlarged unrestrained shape. The fibrous body 18 incorporates a great multitude of individual fibers which form a tremendous number of small interstitial spaces throughout its mass, and these individual fibers arecoated with abiologically harmless anti-foam agent, such as methylpolysiloxane resin or The means for withdrawing the resulting oxygenated arterial blood comprises a short tubular conduit 19 integral with and normal to the cylinder 7 and located in a position to drain the lowest point of the annular space 14.

The apparatus is provided with an open top 20 in the shape of an annulus, having a flange. The top 20 is formed as a separate piece and is separated from the cylinder 7 by an annular gasket 23;. When assembled, the blood oxygenating apparatus'is held together as one piece by a plurality of long bolts 24 which are firmly attached to the base 5 and pass through apertures 25 in the flange of the top 20 which is clamped firmly to the cylinder 7 by means of thumb screws 26 which are screwed on to the threaded upper ends 27- of the bolts 24. In order to prevent any foreign objects from entering, the apparatus through the open top 20 when in use, without interfering with the free passage of air, a piece of gauze 21 or similar material may be stretched across its upper rim and held in place by a rubber band 22. Itshould be noted that as a safety measure the base 5 may be constructed with a relatively large surface area and. weight compared to the overall size and weight of the apparatus, so that the apparatus will be very stable and unlikely to tip over. The use ofthumb screws makes it very easy to disassemble the apparatus into its component parts, and the parts may be made of materials that permit autoclaving.

In use, the oxygenating apparatus is set up as shown schematically in the drawings (Fig. 1). A flexible conduit 28 is introduced into a vessel of the circulatory system of a human being or animal 29 to withdraw its venous blood, and a blood pump; 31 having an intake and an outlet with adjustable speed. controls is employed in series with the flexible. conduit 28 to pumpjthe venous blood from the living subject 29 into the venous blood inlet 9 of the apparatus. A second flexible conduit 32 is connected to the arterial blood outlet 19 at one end and to a vessel in the circulatory system of the living subject at its other end, and a second blood pump 33 is employed in series with the second flexible conduit 32 to provide pump pressure for the withdrawal of arterial blood from the apparatus and for the return of the arterial blood to the body of the subject 29. A third flexible conduit 34, connected to the oxygen inlet 8, is used to introduce oxygen into the apparatus under a predetermined pressure from an oxygen source, such as a pressure cylinder.

In operation, oxygen is introduced into the blood oxygenating apparatus through the oxygen inlet 8 under a predetermined pressure. The pressurized oxygen fills the chamber 6 in the base 5 and due to its pressure forces its way through the hydrophilic microporous filter disc which has a controlled maximum pore size and its pores uniformly distributed throughout its mass. As the pressurized oxygen passes through the microporous filter disc 10, it emerges as innumerable microscopic jets of oxygen on the upper surface of the filter disc 10. The venous A blood from the living subject is injected under pump pressure into the lower chamber 17 of the cylinder 7 through the venous blood inlet 9. Due to the position of the venous blood inlet 9 integral with the wall of the cylinder 7 and tangential to its circular cross section (Fig. 3), the blood swirls around the inner wall of the lower chamber 17 immediately upon entering it, and a general condition of turbulence is created in the blood occupying the volume of the lower chamber 17. The blood swirling in the lower chamber 17 passes over the jets of oxygen on the upper surface of the filter disc 10. The microscopic nature of the oxygen jets uniformly distributed across the upper surface of the filter disc 10 and the turbulence of the swirling blood are conditions which combine to insure that an enormous number of minute bubbles of oxygen are formed throughout the blood introduced into the lower chamber 17. The oxygen bubbles in the blood are so tiny that they may be characterized as mist-like in proportion, and they are so thoroughly intermixed with the blood that the entire volume of the blood acts as the equivalent of one huge interface, whereby interface is meant the surface forming a boundary between a gas and a liquid where the gas is in the form of a bubble within the liquid. This huge interface, which in reality is an immeasurable number of tiny interfaces, has the same efiect in exposing the blood to the oxygen that would be achieved if the blood could be spread in an infinitely thin layer over a tremendous surface area and exposed to oxygen while so spread. Thus, the dispersion of the oxygen in mist-like bubbles throughout the entire mass of blood in the instant invention achieves much more eflicaciously in a bubbling method what has been sought to be achieved for years by the prior art devices in which the blood was in fact thinly spread v V &

over a large surface area or in which a few and'large bubbles were passed through the blood; and yet, in the present invention oxygenation is accomplished in an infinitely better fashion by a surprisingly simple device with no moving parts which is much less expensive and com plex and much more trouble-free than the-prior art devices.

Of course, it was the failure to provide a successful means for ridding the blood of gas bubbles which caused abandonment of all prior attempts to oxygenate blood by variations of the method of bubbling oxygen through it, for if any gas bubbles remain in the arterial blood which is returned to the circulatory system .of the living subject, air embolism will occur with fatal results. However, in the present invention the oxygenated blood in.

the lower chamber 17 which is infused with minute bubbles' of gas comprising both excess oxygen and the carbon i dioxide which is released as a' waste product, is forced up into the fibrous body 18 by the pressure of the blood entering the lower chamber 17 until it is eventually forced to rise through the entire height of the fibrous body 18 and emerges at the top of tube 13. As the blood rises upward through the fibrous body 18, the combination of the enormous number of-small interstitial spaces formed by the fibers of the fibrous body 18 and the anti-foaming coating on the individual fibers causes the surface tension phenomenon of coalescence to take-place.

The interfaces of the minute gas bubbles are broken as the blood rises, and this causes these individual bubbles to progressively coalesce forming larger and larger bubbles until When the surface level of the blood in the apparatus is reached, the relatively large bubbles, which have resulted from the coalescence of great numbers of the original minute bubbles, are so large that the surface tension of their interfaces is no longer sufiicient to hold the bubbles in the blood, and they burst free into the upper chamber of the apparatus which is at atmospheric pressure. The bursting of the bubbles at the surface of the blood is a manifestation of the surface tension phenomenon of liquid-gas separation.

The blood, which becomes free of all gas on reaching the top of the cylindrical tube 13, is caused by gravity and the upward pressure of the blood below it to spill over the top edge of the tube 13 and to occupy the annular space 14 from which it is withdrawn through the arterial blood outlet 19. From the arterial blood outlet 19, the blood is conducted back to the circulatory system of the living subject 29 by the second flexible conduit 32 under pressure supplied by the second blood pump 33 (Fig. 1).

It should be noted that the present invention, by providing a simple, compact, and relatively fool-proof blood oxygenating environment, makes its use especially adaptable to intricate heart surgery or open cardiotomy where the subject is under hypothermia.

Having thus described my invention, what I claim as new and wish to secure by Letters Patent is:

A blood oxygenating apparatus comprising a cylindrical vessel having an upper chamber and a lower chamber, the upper chamber, being divided into an upper and a lower portion and an intermediate portion, an oxygen inlet in the lower chamber for admitting oxygen under pressure, a venous blood inlet in the lower portion of the upper chamber of the vessel tangential to the wall of the vessel for tangentially injecting venous blood from a living subject into the vessel, a microporous porcelain filter disc between the upper chamber and the lower chamber having microscopic pores uniformly distributed throughout its mass to create a great multiplicity of microscopic jets of oxygen emanating from its upper surface and dispersing an immeasurable number of minute oxygenb ubbles throughout a supply of venous blood which is ejected from the tangential blood inlet and swirls over the upper surface of the filter, the oxygen bubbles reacting with the venous blood to oxygenate it and simultaneously release carbon dioxide as a Waste product, a cylindrical tube hav ing an axis coincidental with the axis of the cylindrical vessel positioned in the intermediate portion of the upper chamber, the cylindrical tube having a diameter suifi ciently smaller than the diameter of the cylindrical vessel to create an annular space between the outer surface of the tube and the inner surface of the cylindrical vessel, a support ring integral Withthe wall of the vessel and the wall of the tube for supporting the tube in it desired position and to separate the lower portion of the upper chamber fromthe intermediate portion and to seal the bottom of the annular space from the lower portion of the upper chamber, a closely packed fibrous body having a multitude of individualfibers contained within the cylindrical tube, the fibrous body forming a multitudinous number of small interstitial spaces, individual fibers of the fibrous body being coated with an agent to break down theinterfaces of the minute oxygen and carbon dioxide bubbles, in the blood as it comes into contact with the fibers for causing the minute bubbles to coalesceand form increasingly large bubbles as the blood rises in the cylindrical tube and fibrous body, the resulting large bubbles of oxygen and carbon dioxide being spontaneously released from the blood by bursting upon reaching atmospheric pressure at the surface level of the blood at the top of the cylindrical tube, the upper portion ofthe upper chamber beingprovided with an opening to permit the carbon dioxide Waste product and excess oxygen released from the blood at surface level to pass into the atmosphere, an arterial blood outlet positioned at the lowest point of the annular space for withdrawing resulting oxygenated gas-free arterial blood which spills over the top of the cylindrical tube into the annular space due to gravity and the pressure of the blood rising in the tube, and means for returning resulting arterial blood to the body of the living subject.

References Cited in the file of this patent Clark, Gollan' and Gupta: The oxygenation of blood by gas dispersion, Science, vol. 111, pages -87, Jan. 27, 1950.

Clark, Gupta and Gollan: Dispersion oxygenation, Proceedings of the Society for Experimental Biology and Medicine, vol. 74, No. 2, pages 268-271, June 1950.

Clark, Hooven and Gollan: A large capacity all-glass dispersion oxygenator and pump, Review of Scientific Instruments, vol. 23,No. 12, pages 748753, December 1952. 

